EP4013629B1

EP4013629B1 - A process for manufacturing a noise reducing layer and a tyre comprising said noise reducing layer

Info

Publication number: EP4013629B1
Application number: EP20744134.6A
Authority: EP
Inventors: Robin Arends; Roberto Pontone; Cristian CAPALDI; Gaetano Fortunato; Luca CAMOSI
Original assignee: Bridgestone Europe NV SA
Current assignee: Bridgestone Europe NV SA
Priority date: 2019-08-12
Filing date: 2020-07-22
Publication date: 2024-02-21
Anticipated expiration: 2040-07-22
Also published as: EP4013629A1; ES2975424T3; WO2021028747A1

Description

The invention relates to a process for manufacturing a noise reducing layer. Furthermore, the invention relates to a tyre comprising the noise reducing layer housed in the inner cavity of the tyre.
One of the noises produced by a tyre in use is the resonance noise of the cavity generated by the vibration of air under pressure inside the inner cavity of the tyre.
In particular, the rolling of the tyre on a surface with a macro-roughness excites the air inside the tyre. The column of air trapped in the tyre has its own natural modes.
Its first natural mode, called cavity mode, ranges between 180 and 250 Hz for a typical passenger car tyre, depending on the size of the envelope. When the column of air starts resonating, it creates acoustic pressure on the wheel, which causes it to vibrate. The wheel then transmits its vibrations to hub of the wheel, then to the passenger compartment through structure-borne propagation. The cavity noise perceived inside the car usually resembles the one of a panpipe and it is known as cavity resonance noise. To reduce this type of noise, the use of a porous material applied to the surface of the impermeable layer of the inner cavity of the cavity, so that the cavity resonance noise is reduced by the porous material, has long been known. The porous material works by reducing the section available to the propagating pressure waves and contributes by dissipating the pressure waves.
In case the sealing action and the noise reducing action need to be combined in one single tyre, its inner cavity has to simultaneously house both the sealant layer and the noise reducing layer. Obviously, taking into account the mechanism with which the sealant layer operates, experimented solutions have adopted a sealant layer arranged in contact with an air impermeable layer and a foam material layer arranged, in turn, in contact with the sealant layer on the opposite side relative to the air impermeable layer.
Herein and below, for "air impermeable layer" we mean a layer substantially impermeable to air, and used in tubeless tyres in order to make sure that the air inside the carcass remains as much as possible under pressure.
These solutions turned out to be ineffective because, as prior art documents (e.g. WO2017/076531 ) pointed out, the foam material physically interacts with the sealant layer and forbid the flowability of the sealant.
DE202010005400 discloses a tire comprising a tire cavity enclosed by a running strip supporting the tread surface and a noise dampening insert or a noise dampening insert arrangement disposed in the cavity.
US3425890 discloses the production of plastic foam materials in which the foam is distorted and heat set in the distorted state wherein the distortion arises from stretching and/or compressing the foam.
WO2019129584 discloses a pneumatic tyre comprising an inner surface of the tyre, wherein a sound absorbing device component is connected to the inner surface of the tyre and comprises a panel with a plurality of perforations and two sidewall sections.
US2006157180 discloses a low noise pneumatic tire where a band-shaped sound absorbing material formed of a porous material whose apparent density defined in JIS K6400 is in a range of 10 to 70 kg/m3, is attached on the inner surface of a tread by use of an elastic fixing band.
GB2483255 discloses a tyre cavity noise absorber comprising a sound absorbing body and a support wherein the absorber is arranged such that, when installed in a tyre cavity and the tyre is stationary, the support supports the sound absorbing body in a position spaced from the inside circumferential wall of the tyre.
Therefore, there is a strong need to rely on a solution that allows manufacturers to use, in the inner cavity of a tyre, both the sealant layer and the noise reducing element, leaving, at the same time, the respective sealing and noise reducing properties unchanged.
The inventors of this invention offer an effective noise reducing layer that can be used alone or together with a sealant layer, without suffering from the above-mentioned drawback of the prior art.
The subject-matter of the invention is a process for manufacturing a noise reducing layer designed to be housed inside the cavity of a tyre; said process being characterized in that it comprises:

a stacking step, during which a stack of fibre-reinforced rubber or pre-preg layers is created, in which between one layer and the other there is interposed a plurality of anti-sticking elements spaced apart from one another; said anti-sticking elements being arranged in a staggered position along the two faces of a same fibre-reinforced rubber or pre-preg layer;
a vulcanization step, during which said stack (1) of fibre-reinforced rubber or pre-preg layers is subjected to a compacting pressure and to a fibre-reinforced rubber or pre-preg vulcanization temperature;

Hereinafter by "anti-sticking element" we mean a material that, when placed between two rubber layers, prevents said rubber layers, during the vulcanization step, from being subjected to chemical bonds, thus being glued to one another.
The use of the anti-sticking element in the liquid state is preferred as it ensures a quicker and more effective removal thereof at the end of the manufacturing of the fibre-reinforced rubber or pre-preg structure.
The anti-sticking elements are arranged between the rubber layers and are preferably spaced apart from one another by a same distance and are staggered by half said distance along two opposite faces of a same fibre-reinforced rubber or pre-preg layer.
By so doing, a honeycomb fibre-reinforced rubber or pre-preg structure can be obtained.
Said compacting pressure preferably ranges from 1.5 to 2.5 MPa.
Preferably, the fibre-reinforced rubber or pre-preg structure comprises a fibre fabric consisting of a plurality of cords parallel to one another; more preferably, the fibre-reinforced rubber comprises a fibre fabric with a net structure; even more the fibre-reinforced rubber or pre-preg comprises a fibre fabric with a net structure in which the cords intersect one another at a right angle.
The fibre fabric with a plurality of cords parallel to one another or, even better, with a net structure in which the cords intersect one another at a right angle is preferred as, during the manufacturing of the fibre-reinforced rubber or pre-preg structure, it ensures a better structural resistance when it undergoes a great compression during the vulcanization step.
Preferably, said fibre is Nylon.
Preferably, the fibre-reinforced rubber or pre-preg structure has a honeycomb structure.
A further subject-matter of the invention is a pneumatic tyre comprising a tread, a carcass defining an inner cavity and a noise reducing layer, which is arranged in said inner cavity in the area of the tread; said tyre being characterized in that the noise reducing layer comprises a fibre-reinforced rubber or pre-preg structure with through cells; said through cells of having a cross area ranging from 100 to 20000 mm²; said fibre-reinforced rubber or pre-preg structure having a height ranging from 15 to 40 mm.
More preferably, said through cells have a cross area ranging from 500 to 9000 mm²; even more preferably said cells have a cross area ranging from 1000 to 5000 mm².
Preferably, the fibre-reinforced rubber or pre-preg structure has a height ranging from 20 to 35 mm.
Preferably, the fibre-reinforced rubber or pre-preg structure comprises a fibre fabric consisting of a plurality of cords parallel to one another; more preferably, the fibre-reinforced rubber or pre-preg comprises a fibre fabric with a net structure; even more preferably, the fibre-reinforced rubber or pre-preg comprises a fibre fabric with a net structure in which the cords intersect one another at a right angle.
Preferably, the fibre is Nylon.
Preferably, the fibre-reinforced rubber or pre-preg structure has a honeycomb structure.
Preferably, said noise-reducing layer comprises foam material layer placed to cover a surface of said grid facing the inner cavity. Preferably, said foam material is made of polyurethane.
Preferably, said noise-reducing layer comprises a membrane or plate placed to cover a surface of said grid facing the inner cavity. More preferably, said membrane or plate is perforated. Even more preferably, said perforated membrane or plate is made of expanded polypropylene.
Preferably, the pneumatic tyre comprises a sealant layer placed between an air impermeable layer and said noise reducing layer.
Hereinafter you can find the description of embodiments of the invention, by mere way of example, with the aid of the accompanying figures, wherein:

figure 1 shows a semi-finished product of the fibre-reinforced rubber structure according to the invention; and
figure 2 shows the fibre-reinforced rubber structure according to the invention.
figure 3 shows a first embodiment of the invention;
figure 4 shows the embodiment of figure 3 with the presence of a sealant layer;
figure 5 shows a second embodiment of the invention;
figure 6 shows a third embodiment of the invention;
figure 7 shows a fourth embodiment of the invention;

The example below uses a fibre-reinforced rubber structure consisting of a 6.6 Nylon fabric with a net structure in which the cords intersect one another at a right angle and of a rubber layer which incorporates said fabric and whose composition in phr is shown in Table I. Table I

NR 60

SBR 40

CB 48

Sulphur 1.4

Accelerator 1.3
Six layers made of the above-mentioned fibre-reinforced rubber and with a thickness of 1.5 mm were stacked on top of one another so as to form a stack according to figure 1, where it is indicated with number 1.
A plurality of anti-sticking elements 2 were interposed between one layer and the other, so as to avoid, during the vulcanization, the creation of a chemical bond between two adjacent layers and, hence, a gluing thereof. In particular, the anti-sticking elements used is a silicon spray which is marketed with the trade name "RESINA P8".
The stack 1 was inserted into a suitable mould, where it was subjected to a pressure of 2 MPa and to a temperature of 145°C for an amount of time of 30 min.
After the vulcanization step, the stack 1 was opened by pulling the two end layers in opposite directions, thus obtaining the fibre-reinforced rubber structure 3 according to the invention.
The fibre-reinforced rubber structure 3 is a honeycomb structure with cells with a hexagonal shape, each having a cross area of 900 mm² and a height of 30 mm.
As can be evident to a skilled man of the art, the above method can be effectively repeated using a pre-preg material.
In figure 3, number 4 indicates, as a whole, a tyre according to the invention. The tyre 4 comprises a tread 5, a carcass 6 defining an inner cavity 7 of the tyre 4, an inner-liner 8 facing the inner cavity 7 and designed to make sure that the air contained in the inner cavity 7 remains under pressure, and the fibre-reinforced rubber structure 3 arranged inside the cavity 7 in order to attenuate the resonance cavity noise generated by the operating tyre.
The fibre-reinforced rubber structure 3 comprises a honeycomb structure defining a plurality of through cells.
In the other figures (3 - 7) the parts of the respective tyres identical to those of the tyre 4 will be indicated with the same numerical reference and will not be described again.
Figure 4 shows a tyre 11 that differs from that of figure 3 only by the presence of a sealant layer 12.
Figure 5 shows a tyre 13 that differs from that of figure 3 only by the presence of a membrane 14 placed to cover a surface of said grid facing the inner cavity 7.
Figure 6 shows a tyre 15 that differs from that of figure 3 only by the presence of a perforated membrane 16 placed to cover a surface of said grid facing the inner cavity 7.
The materials and the thickness of membrane 14 and the perforated membrane 16 can be decided according to purposes. For example, it can be made of expanded polypropylene-and are 3 mm-thick.
Figure 7 shows a tyre 17 that differs from that of figure 3 only by the presence of a foam material layer 18 made of polyurethane and placed to cover a surface of said grid facing the inner cavity 7.
When a grid structure of the invention is laid down in the tyre cavity, it can work as the noise reducer. Additionally, when put the grid structure on the sealant layer surface, it covers only a minimal fraction of the sealant area, typically less than 5%. That means that the sealant is free from impediments in the remaining 95% of the area. When a puncture occurs in the area where the grid structure of the invention is present, sealing performances are still guaranteed by the repairing sealant flow coming from the surrounding cells free surface areas.

Claims

A process for manufacturing a noise reducing layer designed to be housed inside the cavity of a tyre; said process being characterized in that it comprises:
- a stacking step, during which a stack (1) of fibre-reinforced rubber or pre-preg layers is created, in which between one layer and the other there is interposed a plurality of anti-sticking elements (2) spaced apart from one another; said anti-sticking elements being arranged in a staggered position along the two faces of a same fibre-reinforced rubber or pre-preg layer;

- a vulcanization step, during which said stack (1) of fibre-reinforced rubber or pre-preg layers is subjected to a compacting pressure and to a fibre-reinforced rubber vulcanization temperature;
said anti-sticking elements (2) being in a liquid state.
A process according to one of the claims 1, characterized in that the anti-sticking elements arranged between the fibre-reinforced rubber or pre-preg layers are spaced apart from one another by a same distance and are staggered by half said distance along two opposite faces of a same fibre-reinforced rubber or pre-preg layer.
A process according to claim 1 or 2, characterized in that said fibre-reinforced rubber or pre-preg structure comprises a fibre fabric consisting of a plurality of cords parallel to one another.
A process according to claim 3, characterized in that the fibre-reinforced rubber or pre-preg comprises a fibre fabric with a net structure.
A process according to claim 4, characterized in that said fibre-reinforced rubber or pre-preg comprises a fibre fabric with a net structure in which the cords intersect one another at a right angle.
A process according to one of the preceding claims, characterized in that said fibre is Nylon.
A process according to one of the preceding claims, characterized in that said fibre-reinforced rubber or pre-preg structure (3) has a honeycomb structure.
A pneumatic tyre (4) comprising a tread (5), a carcass (6) defining an inner cavity (7) and a noise reducing layer, which is arranged in said inner cavity in the area of the tread; said tyre being characterized in that the noise reducing layer comprises a fibre-reinforced rubber or pre-preg structure (3) with through cells; said through cells having a cross area ranging from 100 to 20000 mm²; said fibre-reinforced rubber or pre-preg structure (3) having a height ranging from 15 to 40 mm and a width ranging from 45 to 85% relative to the width of the tread.
A pneumatic tyre according to claim 8, characterized in that said through cells have a cross area ranging from 500 and 9000.
A pneumatic tyre according to claim 9, characterized in that said through cells have a cross area ranging from 1000 to 5000 mm².
A pneumatic tyre according to one of the claim from 8 to 10, characterized in that said fibre-reinforced rubber or pre-preg structure (3) has an height from 20 to 35 mm and a width comprised between 55 and 80% of a tread width.
A pneumatic tyre according to one of the claim from 8 to 11, characterized in that said fibre-reinforced rubber or pre-preg structure (3) has a polygonal structure.
A pneumatic tyre according to one of the claims 8 to 12, characterized in that said fibre-reinforced rubber or pre-preg structure (3) has a honeycomb structure.
A pneumatic tyre according to one of the claims 8 to 13, characterized in that said fibre-reinforced rubber or pre-preg structure comprises a fibre fabric consisting of a plurality of cords parallel to one another.
A pneumatic tyre according to claim 14, characterized in that said fibre-reinforced rubber or pre-preg comprises a fibre fabric with a net structure in which the cords intersect one another at a right angle.
A pneumatic tyre according to one of the claims 8 to 15, characterized in that said fibre is Nylon.
A pneumatic tyre according to one of the claims 8 to 16, characterized by comprising a foam material layer (18) placed to cover a surface of said fibre-reinforced rubber or pre-preg structure (3) facing the inner cavity (7) .
A pneumatic tyre according to claim 17,
characterized in that said foam material layer (18) is made of polyurethane.
A pneumatic tyre according to one of the claims 8 to 16, characterized by comprising a membrane or plate placed (14; 16) to cover a surface of said fibre-reinforced rubber or pre-preg structure (3) facing the inner cavity (7).
A pneumatic tyre according to claim 19, characterized in that said membrane or plate (16) is perforated.
A pneumatic tyre according to claim 19 or 20, characterized in that membrane or plate (14; 16) is made of expanded PET, PE, PP, PU, PA.
A pneumatic tyre according to one of the claims 8 to 21, characterized by comprising a sealant layer (12) placed between said inner-liner (8) and fibre-reinforced rubber or pre-preg structure (3).